Alphabet shares fell 8% on Wednesday as investors balked at the Google parent's slowing cloud growth and planned $75 billion capital spending for the year, underscoring growing fears over Big Tech's escalating artificial intelligence costs.

AWS has not been able to match the growth of Amazon’s competitors, with Microsoft Corp.’s Azure and Alphabet Inc.’s Google Cloud seeing cloud-related revenue rise by 31% and 30%, respectively. Even so, AWS remains much bigger than any other cloud infrastructure provider, and it’s notable that those peers also missed expectations this week.

Amazon.com topped Wall Street estimates for quarterly revenue on Thursday, as strong sales over the holiday shopping season boosted its retail business, helping offset weakness in the cloud computing unit.